Mach–Zehnder interferometric analysis of planar polymer waveguide having an adlayer of WS2 for biosensing applications

Abstract

Abstract To enhance the sensing performance of a four-layer planar polymer optical waveguide, an adlayer of tungsten disulfide material is introduced. Also, the proposed waveguide is used to demonstrate theoretically the detection of uric acid concentration in blood or urine. The heterostructure of two-dimensional WS2 offers excellent dry lubricity with respect to any other 2D substance, such as graphite or molybdenum disulfide. The proposed waveguide is analyzed using the common path Mach–Zehnder interferometric method. The dispersion characteristic i.e., the effective refractive indices and thickness of proposed waveguide is plotted for a particular wavelength range to optimize the thickness of film layer. The difference in propagation constant and output interference signal for changing the cover medium is calculated. Using the output interference signal, the phase sensitivity 213 degree/RIU is obtained in the proposed waveguide. The maximum obtained sensitivity, limit of detection and limit of quantification for uric acid concentration in the proposed waveguide structure is 6.86 × 10−2 degree mM−1, 0.061 mM and 0.203 mM, respectively.